Method for operating an automated vehicle convoy

ABSTRACT

A method for operating an automated vehicle convoy, including the steps: periodically wirelessly transmitting messages from preceding participants of the automated vehicle convoy to respective following participants of the automated vehicle convoy, proceeding from the leading participant of the automated vehicle convoy; the messages including at least one piece of, in particular temporal, information from which a minimum distance between each following participant and the respective preceding participant is ascertained; the following participants of the automated vehicle convoy being guided corresponding to the ascertained minimum distance.

CROSS REFERENCE

The present application claims the benefit under 35 U.S.C. § 119 of German Patent Application No. DE 102018205842.3 filed on Apr. 17, 2018, which is expressly incorporated herein by reference in its entirety.

FIELD

The present invention relates to a method for operating an automated vehicle convoy. The present invention furthermore relates to a device for operating an automated vehicle convoy. The present invention furthermore relates to a computer program product.

BACKGROUND INFORMATION

Conventional systems include systems in which vehicles form automated convoys (“vehicle platoons”), in particular on expressways. Vehicles gather behind one another in the process and drive at close distances over limited periods of time at a uniform speed. The coordination for forming, maintaining and dissolving a vehicle platoon takes place with the aid of vehicle-to-vehicle communication. Conventional approaches allow, with the aid of vehicle-to-vehicle communication, all vehicles in the platoon to start or stop together (jam-platoon with shared longitudinal control). This results in a strong improvement in the flow of traffic and in the potential to disperse existing congestions more quickly. The shared driving in the platoon may furthermore save fuel and avoid rear-end collisions.

With the aid of the platooning, it is possible to achieve significant fuel savings. For this purpose, the vehicles must drive so closely in succession that they must be coupled to one another via an “electronic drawbar,” i.e., must communicate with one another in real time, e.g., for the transmission of steering and brake signals.

German Patent Application No. DE 10 2010 008 208 A1 describes a method for preventing collisions between vehicles, an emergency brake application of one vehicle being mitigated if a collision with the following vehicle is imminent.

SUMMARY

It is an object of the present invention to provide an improved method for operating an automated vehicle convoy.

According to a first aspect of the present invention, the object may be achieved by an example method for operating an automated vehicle convoy, including the steps:

-   -   periodically wirelessly transmitting messages from preceding         participants of the automated vehicle convoy to respective         following participants of the automated vehicle convoy,         proceeding from the leading participant of the automated vehicle         convoy;     -   the messages including at least one piece of, in particular         temporal, information from which a minimum distance between each         following participant and the respective preceding participant         is ascertained;     -   the following participants of the automated vehicle convoy being         guided corresponding to the ascertained minimum distance.

In this way a method is provided in which each platoon participant knows how long he or she may continue to drive within the automated vehicle convoy. A so-called “time stamp” is used in the process to transmit the necessary pieces of information. In this way, a defined distance may be provided between the vehicles, which in some circumstances is even below a minimum distance prescribed by law between the vehicles of the automated vehicle convoy. This is achieved by a cyclical unidirectional flow of information, proceeding from the leading vehicle to the rear and starting from the leading vehicle again.

According to a second aspect of the present invention, the object may be achieved by an example device for the optimized operation of an automated vehicle convoy, including:

-   -   a transmitting device for periodically wirelessly transmitting         messages from preceding participants of the automated vehicle         convoy to respective following participants of the automated         vehicle convoy, proceeding from the leading participant of the         automated vehicle convoy;     -   the messages including at least one piece of, in particular         temporal, information from which a minimum distance between the         following participant and the respective preceding participant         is ascertained; and     -   a guiding device for guiding the participants of the automated         vehicle convoy corresponding to the ascertained minimum         distance.

A guiding of a participant of the automated vehicle convoy may be understood to mean a control of a drive unit or a brake unit of the participant to adapt or set a spatial distance from a preceding participant.

Advantageous refinements of the example method according to the present invention are described herein.

One advantageous refinement of the example method according to the present invention provides that the following participants may only evaluate messages transmitted by the directly preceding participant. In this way, a safety level is advantageously enhanced by a “hop by hop communication” since each involved vehicle, upon receipt of a message, knows that all preceding vehicles have received the respective message of the vehicle preceding them within the same periodic passage or, expressed in more general terms, that all preceding vehicles have received valid messages.

One further advantageous refinement of the example method according to the present invention provides that the piece of, in particular temporal, information includes at least one of the following pieces of information: stopping distances of the participants, uncertainty of stopping distances of the participants, differences in the stopping distances of the participants, validity or validity period of the message, distance which the follower may maximally drive during the validity of the message, braking profiles of the participants, response time of the brakes of the participants. Optional attributes are thereby transmitted, which may further improve an automated operation of the automated vehicle convoy.

One further advantageous refinement of the example method according to the present invention provides that the message cannot be undone by the transmitting participants. This prevents the event that, in some circumstances, the undone messages are not received, whereby in some instances collisions occur between the participants.

One further advantageous refinement of the example method according to the present invention provides that the message is transmitted again, or a new message is transmitted, by the preceding participant in the event that the message was not received by the following participant.

One further advantageous refinement of the example method according to the present invention is characterized in that time intervals at which messages are transmitted are shorter than a validity period of the piece of, in particular temporal, information contained therein. In other words, this means that a time interval between the sending or transmission of two chronologically consecutive messages is smaller than the validity period of the information contained therein. A safety level is also advantageously increased in this way since not every message is necessarily required to continuously maintain the driving operation of the automated vehicle convoy. As a result, a further safety measure is thereby implemented.

One further advantageous refinement of the example method according to the present invention provides that pieces of information regarding the number of participants of the automated vehicle convoy are transmitted in the messages. In this way a simple principle is implemented, with the aid of which a length of the automated vehicle convoy is limitable, a counter is incremented by one in each case by each participant.

One further advantageous refinement of the example method according to the present invention provides for the messages to be signed in a defined manner. In other words, this means that the messages may be unambiguously assigned to a participant transmitting the message or sending the message. In this way, a security of the message exchange between the participants of the automated vehicle convoy is further increased.

One further advantageous refinement of the example method according to the present invention provides that a pseudo random number, which is transferred to a hash function, is generated with the aid of the pieces of temporal information and a symmetric key, a result of the hash function being attached to the message. A hash function may be understood to mean a function which maps a larger input set onto a smaller target set. In this way, simple measures of conventional cryptography which are efficient in terms of time are applied to still further increase the security of the message transmission between the participants of the automated vehicle convoy.

One further advantageous refinement of the example method according to the present invention provides that the hash function is resistant against length extension attacks. For example, the hash function may be a conventional SHA3 function which is resistant against so-called length extension attacks. In this way, it is advantageously supported that false messages, manipulation attempts and transmission errors may be identified. Transmission errors caused e.g., by a disrupted transmission channel may also be identified by hash functions which are not resistant against length extension attacks.

The present invention is described in greater detail hereafter with further features and advantages based on several figures. All described or illustrated features, either alone or in any arbitrary combination, form the subject matter of the present invention, regardless of the wording or representation thereof in the description or in the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of an operating mode of one specific embodiment of a provided method for operating an automated vehicle convoy.

FIG. 2 shows a schematic representation of an operating mode of one improved specific embodiment of the provided method for operating an automated vehicle convoy.

FIG. 3 shows a schematic representation of a method for signing messages between the participants of the automated vehicle convoy.

FIG. 4 shows a schematic block diagram of a device for operating an automated vehicle convoy.

FIG. 5 shows a schematic sequence of one specific embodiment of the provided method for operating an automated vehicle convoy.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Hereafter, the term ‘automated vehicle’ is used synonymously to mean semi-automated vehicle, autonomous vehicle and semi-autonomous vehicle.

In particular, it is a core aspect of the present invention to provide an improved method and a device for operating an automated vehicle convoy.

Automated vehicle convoys (“platoons”) are generally made up of multiple, functionally coupled vehicles which follow in close succession and are operated in an automated manner. It is provided to minimize distances between the participants of the automated vehicle convoy in such a way that minimum distances between the participants of the automated vehicle convoy are considerably shorter than stopping distances. The distances are at least as large as the differences in the stopping distances of participants driving in succession. This is necessary, in particular, for high density vehicle platooning in which the participants drive at minimal distances from one another to reduce fuel consumption and increase driving efficiency.

With the provided method, it is advantageously possible to provide a safe driving operation also in the case of an unexpected interruption in communication between the participants of the automated vehicle convoy.

The present invention provides a unidirectional message flow between the participants of the automated vehicle convoy, messages being transmitted in each case from preceding participants to the following participants of the automated vehicle convoy.

FIG. 1 shows a principle of such a message flow. An automated vehicle convoy 100 including three participants 10 a, 10 b and 10 c is apparent. Participant 10 a represents the leading vehicle of automated vehicle convoy 100, participant 10 b following participant 10 a at a distance d_(v) (“minimum distance”), which is shorter than is usually provided for safe driving. The distances and message flows described hereafter are described by way of example for participants 10 a, 10 b, but apply analogously also to all further participants of automated vehicle convoy 100. The number three used to describe the participants of automated vehicle convoy 100 in FIG. 1 is only by way of example, of course.

To ensure safe stopping in the event of an emergency brake application, participant 10 a transmits periodic messages M1 to participant 10 b which each include at least one “time stamp” defining a validity period of the message of participant 10 a. In this way, participant 10 b knows the distance he or she has available in the event of an emergency braking maneuver of participant 10 a, in addition to minimum distance d_(v).

The described messages are thus transmitted, proceeding from participant 10 a, in a chain-like manner from one participant of automated vehicle convoy 100 to the next (“from the front to the rear”). In principle, however, it is also possible that following participants generate the messages at a different frequency and at different points in time. It is thus only necessary that the time stamps used in the messages and, if necessary, further attributes are selected in such a way that the automated vehicle convoy is always in a safe state.

Hereafter, further optional pieces of information are described, which may be transmitted in addition to the above-mentioned information regarding the stopping distance.

Message M₁ may also include pieces of information regarding a driving distance d_(d1) (e.g., in the form of a distance dimension, a piece of temporal information, a geo position, etc.) and a time stamp t₁, which preferably defines an absolute point in time in the future. In the simplest case, driving distance d_(d1) may be calculated from the instantaneous speed and the time until time stamp t₁ is reached. A transmission of relative times of participants 10 a, 10 b would also be conceivable here. These two parameters determine the maximum distance which participant 10 b may drive until the time of time stamp t₁ has been reached. If no new message including a new time stamp which is in the future was received by the expiration of this time stamp t₁, a procedure must be initiated to maintain a safe driving state without communication between participants 10 a, 10 b, e.g., in the form of an initiation of an emergency brake application.

In the event that the time of time stamp t₁ has been reached, but the distance between participants 10 a, 10 b is shorter than d_(d1), participant 10 b is not permitted to continue driving, so that participant 10 b has to initiate a procedure to maintain the safe driving state. d_(d1) thus represents an optional attribute, with the aid of which changing speeds of participant 10 a may be taken into consideration better by participant 10 b.

Stopping distance d_(b1) thus represents an optional attribute to be able to respond better to a driving behavior of the preceding driver. Pieces of information regarding stopping distance d_(b1) may be designed e.g., as a piece of distance information, a piece of temporal information, a piece of information including absolute coordinates, etc.

In this way, the two described optional parameters t₁, d_(d1) define an upper, average speed limit for participant 10 b.

Based on the described three parameters d_(b1), t₁ and d_(d1), participant 10 b is able to ascertain minimum driving distance d_(v). Initially, participant 10 b ascertains his or her own stopping distance d_(b2) (not shown). In the event that

Δ_(b) =d _(b2) −d _(b1)

d_(b1) . . . stopping distance of participant 10 a

d_(b2) . . . stopping distance of participant 10 b

is positive, this difference must be taken into consideration in the calculation of driving distance d_(v) to depict the longer necessary stopping distance.

In the event that

Δ_(b) =d _(b2) −d _(b1)

is negative, difference Δ_(b) does not reduce the necessary minimum driving distance d_(v) since the shorter stopping distance of participant 10 b, compared to that of participant 10 a, is not counted at the beginning of the braking process; in this case, difference Δ_(b) is thus set to zero.

Dead times and a variance in the brake application sensitivity of the host braking system are converted into a distance d_(t), based on the speed of participant 10 b. This distance d_(t) may also be taken into consideration in the ascertainment of minimum driving distance d_(v) and may be transmitted as an optional piece of information in message M₁. The deceleration of participants 10 a, 10 b takes place according to a defined temporal braking profile, e.g., when participant 10 b during an emergency braking maneuver brakes less strongly than participant 10 a for a certain time. The distance between two participants 10 a, 10 b may not be sufficient to avoid a collision.

For this reason, either a fixed braking profile may be taken into consideration for all participants, or participant 10 a may describe his or her potential braking profile using parameters which are added to the periodically transmitted messages as optional parameters. Optionally, a degree to which an accuracy of the braking profile is uncertain may also be added to the messages, e.g., in the form of a maximum deviation from the braking profile.

Based on this information, participant 10 b may calculate an additional safety distance d_(p1) to compensate for this uncertainty. In the last step, distance d_(d1) may be taken into consideration in the calculation of minimum driving distance d_(v). This is necessary for the following reasons:

Participant 10 b is allowed to drive distance d_(d1) until the expiration of time stamp t₁. If participant 10 b does not receive a new message M₁′ (not shown), including a new time stamp t₁′>t₁ and a new distance d_(d1)′>0 prior to the expiration of time stamp t₁, he or she must initiate a procedure to maintain the safe driving state, e.g., in the form of an emergency braking maneuver at point in time t₁.

If, for some reason, no pieces of information are able to be transmitted from participant 10 a to participant 10 b, after message M₁ was sent and participant 10 a has initiated the procedure for maintaining a safe driving state at point in time t₀ at which message M₁ was sent, participant 10 b starts a procedure for maintaining a safe driving state at point in time t₁>t₀. During time interval t₁−t₀, participant 10 b drove up to distance d_(d1), therefore this value must be considered in the calculation of minimum driving distance d_(v).

Minimum driving distance d_(v) is then ascertained as follows:

d _(vmin)=Δ_(b) +d _(t)(+d _(p1))+d _(d1)

Value d_(p1) is provided in parentheses since it is optional.

To enable a uniform driving operation of automated vehicle convoy 100, participant 10 a thus periodically transmits new messages, each including an increased time stamp. Respective increased time stamps are only utilized when the time stamps include pieces of absolute time information. The time stamps do not necessarily increase in the case of pieces of relative time information.

This preferably provides a transmission of new messages at a higher frequency than necessary so that a reliability is increased if messages are lost. In the event that following messages are lost, participant 10 b initiates a procedure to maintain a safe driving state and may return to the customary procedure if new messages are received. To enable driving with short distances between participants at high speeds, a high transmission frequency of the message transmission is sought. The messages should be kept as short as possible.

Participant 10 b also generates periodic messages M₂ for following participant 10 c. Messages M₂ include at the most the same time stamps and driving distances from one of the most recently received messages M₁ or alternatively time stamps which do not extend so far in to the future, with accordingly shorter driving distances. In this way, a safe state of the automated vehicle convoy may also be ensured in a simple manner in the event of a failure of the communication between the participants. However, a safe state of the automated vehicle convoy must also always be ensured with a suitable selection of time stamps by participant 10 b which are greater than the time stamps in the messages received from participant 10 a. In the event that b₂ (not shown) is greater than b₁, participant 10 b sets the braking distance to b₂. In the event that b₂ is smaller than b₁, the messages may include braking distance b₁. On the other hand, however, participant 10 b then has to adapt his or her braking force so that participant 10 b comes to a standstill after distance b₁ and not after distance b₂.

All participants 10 a . . . 10 n are now permitted to evaluate messages from the respective preceding participant, i.e., that participant 10 b is only allowed to interpret messages M₁ of participant 10 a, and participant 10 c only those of participant 10 b, but not messages of participant 10 a.

This is necessary to provide a safe driving operation of automated vehicle convoy 100. In the event that the communication between participants 10 a, 10 b is interrupted, participant 10 c initiates a procedure for achieving a safe driving state after the last time stamp of received messages M₁ was reached.

In the event that participant 10 c does not receive any messages including newer time stamps from participant 10 b, he or she will conclude that participant 10 b has initiated a procedure for achieving a safe driving state. In this case, participant 10 c initiates a procedure for achieving a safe driving state to prevent a potential collision with participant 10 b, even if he or she is able to receive messages M₁ of participant 10 a. In the event that only the communication between participants 10 b, 10 c is disrupted, not however between participants 10 a, 10 b, participant 10 c initiates the procedure for achieving a safe driving state, while participant 10 b does not carry this out. During a possible braking maneuver, the distance between participants 10 b, 10 c increases continuously. If, during this braking maneuver, the distance between participants 10 b, 10 c becomes sufficiently large for participant 10 c to come to a standstill, participant 10 c may interrupt the braking process since now there is no need any longer to rely on pieces of information from participant 10 b to come to a safe halt.

Optionally, participant 10 a may listen in on messages transmitted from participant 10 b to participant 10 c and initiate a repeat transmission of messages M₁ if he or she has not received any messages M₂ after a defined short time interval t_(a) to deal with a possible loss of information of messages M₁ during the initial transmission, as is indicated in FIG. 2 in principle. Participant 10 a may repeat his or her transmission procedure multiple times to thereby increase the likelihood of a correct reception of the messages by participant 10 b. He or she may use repetition mechanisms (chase combining) to increase the likelihood of a correct reception of the message by participant 10 b.

This repetition mechanism does not need to be negotiated between participants 10 a, 10 b. Participant 10 b may automatically initiate this mechanism when he or she receives first message M₂ and may end this mechanism when he or she does not receive any messages M₂ even after multiple re-transmission attempts.

All messages M₁ . . . M_(n) are preferably cryoptographically signed to ensure that they were sent by the expected participant 10 a . . . 10 n. Since the messages include absolute time stamps, they are immune to replay attacks. In contrast, a re-transmission of messages carried out by whomever may increase the reliability of the overall system. In the event that a defined number of participants is to be present in automated vehicle convoy 100, a participant counter may also be included, which may be attached to every message. Each participant increments this participant counter, compared to the message that he or she received, so that, in this way, participant 10 a has participant counter content “0,” participant 10 b has participant counter content “1” etc. Based on a fixed or a scenario-dependent maximum participant counter, every participant is able to ascertain whether he or she is entitled to receive messages from participants to calculate therefrom a certain minimum driving distance d_(v). If the counter content of the participant counter is greater than or equal to the entire counter content of all received messages, further messages should be ignored, whereby a sufficient distance from the preceding participant is adhered to, without relying on pieces of information which were transmitted from the preceding participant.

FIG. 3 shows such a schematic method, which is conventional, for providing an integrity of messages, which may be utilized to transmit the above-mentioned messages M₁ . . . M_(n). An exemplary message M₁ having a value v, which increases strictly monotonically in the next message, is apparent. In a step 200, a pseudo random number is generated from value v together with a symmetric key. In a further step 210, this pseudo random number is transferred to a hash function for generating a hash value, this hash value being attached to message M₁. The individual optional parameters x1 . . . x4 within message M₁ are apparent, which are also transferred to the hash function so that their integrity may also be checked.

Compared to asymmetric cryptography methods, the use of symmetric cryptographic methods is advantageous since they are particularly efficient and thereby time-efficient.

The provided mechanism proposes a unidirectional communication, i.e., that one unit only sends and one unit only receives. In a defined step, a shared key is negotiated between the sender and the recipient. For example, the sender may utilize the public key of the recipient to encrypt a locally generated pseudo random number and transmit it to the recipient, who is able to decrypt the key using his or her private key. A bidirectional communication may also be used for negotiating the shared key, only the exchange of messages M₁ . . . M_(n) taking place unidirectionally. In a step 200, the pseudo random number is calculated with the aid of the private key and value v.

In a further step 210, the generated key is used by the sender within the signing process. Each message to be transmitted includes a strictly monotonically increasing value v, e.g., in the form of above-mentioned time stamp t₁. As an alternative, value v may also be strictly monotonically decreasing. In any case, the described monotonicity should not change when the mechanism is impaired. Function f uses the secret key and value v as inputs and depicts an output value in the form of a pseudo random number. An exemplary function having the required features may be a shift register. The secret key is used to initialize the shift register, the shift register being shifted for each value v by the number of bits representing the pseudo random number. It is useful to define a fixed minimum increment and to generate a pseudo random number for each value, i.e., for 1, 2, 3, 4, 5, 6, etc., for example. Depending on value v, only a subset of the generated pseudo random numbers is then used, i.e., for 10, 15, 20, 30, 40, for example.

The pseudo random number is generated together with the shared parameters x₁ . . . x_(n) with the aid of a cryptographically safe hash function, which is resistant against length extension attacks, e.g., in the form of a SHA3 function. Optionally, value v may also be included in the hash process. The generated hash value is attached to message M₁, and thereafter message M₁ is transmitted. Optionally transmitted attributes, such as the length of the stopping distance, also have to be transferred to the hash function to be able to ensure their integrity. Upon receipt of message M₁, the recipient carries out the same operations as the sender and compares the resulting hash value. If the two hash values agree, the integrity of message M₁ is confirmed.

The hash value fulfills three different purposes:

-   -   First, it allows an unambiguous identification of the sender.         Since only the sender and the recipient know the shared key, the         recipient may be certain from whom the message stems, as long as         it is ensured that it was not generated by himself or herself.         The sender may decline being the author of a message since it         could potentially also have been generated by the recipient.         Depending on the respective scenario in which the encryption         mechanism is used, however, this is not problematic and is         inherent to symmetric cryptography.     -   Secondly, it is possible to detect transmission errors since, in         general, the calculated hash value thus deviates from the hash         value transmitted in the message. In this case, the hash value         assumes the same functionality as a cyclic redundancy check         (CRC).     -   Thirdly, the hash value ensures that intended changes to the         message content by a third party are reliably detected. Since         the shared secret key is not known to a third party, this third         party is not able to calculate the correct hash value for a         modified message.

By storing value v of the most recently received message and comparing it to value v of the present message, replay attacks may be identified in a simple manner since value v of the present message must be greater (if v is strictly monotonically increasing) or smaller (if v is strictly monotonically decreasing). The secret key may be used to sign many messages as long as the pseudo random numbers are not repeated, e.g., the output of the shift register has a limited period length in which it starts to output the same sequences again, and as long as the value range of v is not exhausted.

When one of the two conditions is met, a new key has to be negotiated between the sender and the recipient since otherwise replay attacks could be successful. If one or multiple message(s) is/are lost during the communication, the recipient is always able to check the integrity of subsequent messages since value v allows it to be synchronized with the sender of accordingly generated pseudo random numbers.

For the described reasons, this mechanism is better suited for unidirectional communication. If a bidirectional communication is to be used, it is recommended to provide two unidirectional communication channels, one for each direction. This includes the sharing of two secret keys and the monitoring of two independent, strictly monotonic values.

FIG. 4 shows a block diagram of a device for operating an automated vehicle convoy 100. A transmitting device 310 is apparent for periodically wirelessly transmitting messages M₁ . . . M_(n) from preceding participants of automated vehicle convoy 100 to respective following participants of automated vehicle convoy 100, proceeding from leading participant 10 a of automated vehicle convoy 100, messages M₁ . . . M_(n) including at least one piece of temporal information from which a minimum distance d_(v) between the following participant and the respective preceding participant is ascertained. A guiding device 320, which is functionally connected to transmitting device 310, for guiding the participants of automated vehicle convoy 100 corresponding to the ascertained minimum distance is also apparent. The described units are designed as electronic control units or parts thereof, for example.

FIG. 5 shows a schematic sequence of a method for operating an automated vehicle convoy 100.

In a step 400, a periodic wireless transmission of messages M₁ . . . M_(n) from preceding participants 10 a . . . 10 n of automated vehicle convoy 100 to respective following participants 10 b . . . 10 n of automated vehicle convoy 100 proceeding from leading participant 10 a of automated vehicle convoy 100 is carried out, messages M₁ . . . M_(n) including at least one piece of temporal information from which a minimum distance d_(v) between each following participant 10 b . . . 10 n and the respective preceding participant 10 a . . . 10 n is ascertained.

In a step 410, a guidance of following participants 10 b . . . 10 n of automated vehicle convoy 100 corresponding to the ascertained minimum distance d_(v) is carried out.

Advantageously, the method according to the present invention may be implemented as software which runs on electronic device 300, for example. This supports an easy adaptability of the method.

Those skilled in the art will suitably modify the features of the present invention and/or combine them with one another, without departing from the core of the present invention. 

What is claimed is:
 1. A method for operating an automated vehicle convoy, comprising: periodically wirelessly transmitting messages from preceding participants of the automated vehicle convoy to respective following participants of the automated vehicle convoy, proceeding from a leading participant of the automated vehicle convoy, the messages including at least one piece of temporal information from which a minimum distance between each following participant and the respective preceding participant is ascertained; and guiding the following participants of the automated vehicle convoy based on the ascertained minimum distance.
 2. The method as recited in claim 1, wherein the following participants may only evaluate messages transmitted by the directly preceding participant.
 3. The method as recited in claim 1, wherein the piece of temporal information includes at least one of the following pieces of information: stopping distances of the participants, uncertainty of stopping distances of the participants, differences in the stopping distances of the participants, validity of the message, distance which the follower may maximally drive during the validity of the message, braking profiles of the participants, response time of the brakes of the participants.
 4. The method as recited in claim 1, wherein the messages cannot be undone by the transmitting participants.
 5. The method as recited in claim 1, wherein in the event that a message was not received by the following participant, the message is transmitted again, or a new message is transmitted, by the preceding participant.
 6. The method as recited in claim 1, wherein time intervals at which messages are transmitted are shorter than a validity period of the piece of temporal information contained therein.
 7. The method as recited in claim 1, wherein pieces of information regarding the number of participants of the automated vehicle convoy are transmitted in the messages.
 8. The method as recited in claim 1, wherein the messages are signed in a defined manner.
 9. The method as recited in claim 8, wherein a pseudo random number, which is transferred to a hash function, is generated with the aid of the pieces of temporal information and a symmetric key, a result of the hash function being attached to the messages.
 10. The method as recited in claim 9, wherein the hash function is resistant against length extension attacks.
 11. A device for operating an automated vehicle convoy, comprising: a transmitting device configured to periodically wirelessly transmitting messages from preceding participants of the automated vehicle convoy to respective following participants of the automated vehicle convoy, proceeding from a leading participant of the automated vehicle convoy, the messages including at least one piece of temporal information from which a minimum distance between each following participant and a respective preceding participant is ascertained; and a guiding device configured to guide the participants of the automated vehicle convoy based on the ascertained minimum distance.
 12. A non-transitory computer-readable data carrier on which is stored computer program including program code for operating an automated vehicle convoy, the computer program, when executed by an electronic device, causing the electronic device to perform: periodically wirelessly transmitting messages from preceding participants of the automated vehicle convoy to respective following participants of the automated vehicle convoy, proceeding from a leading participant of the automated vehicle convoy, the messages including at least one piece of temporal information from which a minimum distance between each following participant and the respective preceding participant is ascertained; and guiding the following participants of the automated vehicle convoy based on the ascertained minimum distance. 